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A072498 n is not equal to the product of the k smallest divisors of n for any k. 3
4, 9, 12, 16, 18, 20, 25, 28, 32, 36, 42, 44, 45, 48, 49, 50, 52, 54, 60, 63, 66, 68, 72, 75, 76, 78, 80, 81, 84, 88, 90, 92, 96, 98, 99, 100, 102, 104, 108, 110, 112, 114, 116, 117, 121, 124, 126, 128, 130, 132, 136, 138, 140, 147, 148, 150, 152, 153, 156, 160, 162 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Positive integers not included in A072510. Sequence includes all squares of primes.

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

EXAMPLE

Divisors of 384 are 1,2,3,4,6,8,12,16,24,32,48,64,96,128,192,384. Partial products are: 1=1, 1*2=2, 1*2*3=6, 1*2*3*4=24, 1*2*3*4*6=144, 1*2*3*4*6*8=1152 and so 384 (144<384<1152) is not in A072510.

MAPLE

filter:= proc(n) local F, d, p;

  F:= sort(convert(numtheory:-divisors(n), list));

  p:= 1:

  for d in F do

    p:= p*d;

    if p > n then return true

    elif p = n then return false

    fi

  od;

end proc:

select(filter, [$1..1000]); # Robert Israel, Sep 28 2016

MATHEMATICA

Select[Range[200], !MemberQ[FoldList[Times, 1, Divisors[#]], #]&] (* Harvey P. Dale, Jun 18 2013 *)

CROSSREFS

Cf. A072510.

Sequence in context: A010386 A094120 A066423 * A162643 A072587 A240112

Adjacent sequences:  A072495 A072496 A072497 * A072499 A072500 A072501

KEYWORD

nonn

AUTHOR

Vladimir Baltic, Aug 03 2002

EXTENSIONS

Edited by Robert Israel, Sep 28 2016

STATUS

approved

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Last modified March 2 09:23 EST 2021. Contains 341746 sequences. (Running on oeis4.)